Dr Lucy Cheke, from the University of Cambridge, told the BBC News website: "The suggestion we're making is that a higher BMI is having some reduction on the vividness of memory, but they're not drawing blanks and having amnesia.

"But if they have a less strong memory of a recent meal, with a less strong impact in the mind, then they may have less ability to regulate how much they eat later on."

Hunger hormones play a huge role in how much we eat, but it is already recognised that our minds have a key role too.

People watching TV while they have their dinner have been shown to eat more or feel hungrier sooner.

And those with amnesia will have repeated meals in a short period of time.

Dr Cheke concluded: "It is too early to talk in terms of advice, but we are certainly beginning to observe the mechanisms that obesity perpetuates itself.

"Concentrating on your food has been a message for a long time, but that may be a bit harder if you're overweight.

"Hopefully knowing what's going on will help us to develop ways of helping people."